Controllable servomotor with balanceable circuit indicator



A. F. DEMING July 4, 1967 CONTROLLABLB SERVOMOTOR WITH BALAI 1(3EABLE CIRCUIT INDICATOR 2 Sheets-Sheet 1 Filed April 27. 1965 26 I04 ID! w 7 l 5 /V 5 m Wm l J M @1 V 5 R 6 mm WE ND W E R D N A G F ATTORNEYS United States Patent 3,329,945 CONTROLLABLE SERVOMOTOR WITH BALANCE- ABLE CIRCUIT INDICATOR Andrew F. Deming, Alliance, Ohio, assignor to Consolidated Electronics Industries Corp., a corporation of Delaware Filed Apr. 27, 1965, Ser. No. 451,157 19 Claims. (Cl. 340-187) The invention relates in general to control systems for servomotors, and more particularly to a control system for first and second balanceable circuits, each independently balanceable with the first having an output to a load and an output to rebalance the first circuit upon unbalance thereof, and the second circuit having an output to an indicator and an output to rebalance the second circuit upon unbalance thereof, with common means to cause unbalance in the two circuits.

The control system of the invention may be used with a servomotor such as a rotatable drive device, and one example of such a servomotor is for use with an antenna rotator which is remotely controllable from a first balanceable circuit. The antenna rotator may be provided with an indicator which is supplied from the output of a second balanceable circuit. A variable impedance is common to both balanceable circuits and is capable of unbalancing each of these circuits. An output is fed back from the rotator to balance the first circuit and a separate output is fed back from the indicator to separately balance the first circuit. I

An object of this invention is to provide a rotator control system wherein an antenna rotator may be remotely controlled through connections on a first terminal strip on the rotator control device, and with a second terminal strip on the rotator control device to which an indicator device may be added at any time, which indicator will move approximately in step with the rotator device and will shut off in synchronism with the rotator device.

A further object of the invention is to provide a separate following indicator unit which may be made of large size so that it may be mounted on the station operator wall and be made so that maps may be secured thereon so that a large motorized sweeping hand will indicate the position of the desired station while maintaining the present small size of the control box for the antenna rotator.

A further object of the invention is to provide an antenna rotator system complete in itself, to which the feature of a separate indicator may be added at any desired time, so that initial purchase of the antenna rotator device and remote control therefor may be made without requiring purchase of the indicator at that time.

A further object of the present invention is to provide a remote control device and indicator device where the indicator requires no special interconnecting cable but may be wired with the same low voltage five-wire cable which is used for the regular interconnection between the rotator and the control device.

A further object of the present invention is to provide a rotator cintrol and indicating system which makes use of a double electrical bridge whereby a single control movable arm of such bridge is made to insure complementary operation of both such bridges, and yet full independence of operation of both bridge circuits is achieved so that synchronism of the rotator is independently achieved from synchronism of an indicator with the control box thereby assuring that inaccuracies of running synchronism between the indicator and rotator motors are corrected at each shut off to insure synchronism of the system.

A further object of the present invention is to provide a system where the indicator mechanism and control 3,329,945 Patented July 4, 1967 mechanism will be initiated only on movement of the control knob and not upon movement of the rotator by wind.

A further object of the present invention is to provide a control system where rotation of the antenna may be stopped at any time by actuating a stop switch and where such stop switch is capable of stopping the operation of both the antenna rotator and the indicating means when such indicating means is used with the device.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a schematic diagram of the invention applied to an antenna rotator, and

FIGURES 2 and 3 are modifications of the invention.

The invention relates to control systems for balanceable circuits and FIGURE 1, for purposes of illustration and not limitation, shows the invention as applied to a control system 12 controlling an antenna rotator 11. The antenna rotator 11 includes a motor 13 to rotate a load such as an antenna 14. This may be an amateur band antenna or a television receiving antenna for connection to a television receiver, not shown. The motor 13 is capable of rotating the antenna 14 to point in any azimuthal direction and an indicator system 15 may optionally be added to the control system 12 to indicate the direction in which the antenna 14 is pointed.

The control system 12 may conveniently take the shape of a small housing, not shown, which may rest upon or near the television receiver. This control system 12 includes a transformer 19 having a primary 18 energizable through a manual switch 20 from an alternating current source 21. The transformer 19 has secondaries 22 and 23, each of which is preferably a low voltage secondary in the order of 24 volts for safety.

The antenna rotator 11 may be a separate housing mounted on the exterior of the dwelling, for example, and carrying the mast of the antenna 14 for rotation of same. The motor 13 may be a reversible induction motor and is shown as having first and second motor windings 24 and 25. These motor windings are energized from the secondary 23 in the control system 12 through conductors 26 and 27. A single-pole double-throw switch 29 is connected in conductor 27 and selectively to the motor windings 24 and 25 through switch contacts 31 and 32. The switch 29 is actuated by a relay 30. A capacitor 36 is connected across the contacts 31 and 32 to provide reversible rotation to the motor 13.

Manual switches 28 and 33 are provided in the conductor 26 between the secondary 23 and the common connection of the motor windings 24 and 25. The manual switch 28 is normally closed and the manual switch 33 is normally open. I

The control system 12 includes a balan'ceable circuit shown as a bridge 40. This bridge 40 is energizable from the transformer secondary 22. The secondary 22 has end terminals 41 and 42 and a midtap 43. The two halves of the secondary 22 on either side of the midtap 43 constitute the first and second legs of the bridge 40. A first impedance 44, shown as a resistor, forms a third leg of the bridge. A first output terminal 45 of the bridge is connected at one end of this first impedance 44. The midtap 43 is the second output terminal of the bridge 40. Variable impedance means are shown in the fourth leg of the bridge connected between terminals 42 and 45. These are illustrated as potentiometers 46 and 47. A conductor 48 connects transformer secondary terminal 42 to a movable blade 49 which divides the potentiometer 46 into first and second complementary impedance sections 51 and 52, respectively. One end of potentiometer 46 is connected by a conductor 50 to the potentiometer 47 and the other end of this potentiometer is connected by a conductor 53 to the bridge output terminal 45. The opposite end of the first impedance 44 is connected to a terminal 54 which is connected through the manual switch 33, conductors 57 and 55 and a normally closed emergency stop switch '56 to the transformer secondary terminal 41. This completes the bridge 40 upon closing of the manual switch 33. The secondary end terminals 41 and 42 may be considered the input terminals of the bridge and the midtap 43 is the second output terminal of the bridge cooperating with the first output terminal 45.

The output of the bridge at terminals 43 and 45 is fed to an amplifier 60 and the output of this amplifier controls the relay and a relay 65. The relay 65 has normally open contacts 66 which are connected in parallel with the manual switch 33. The amplifier 60 may include a transistor 64 as the amplifying device.

The transistor 64 has a base 63, an emitter 66 and a collector 67. The emitter 66 is connected by a conductor 68 to the midtap 43. The collector 67 is connected by a conductor 69 to one end of the relay winding 65 and the other end of this relay is connected through a conductor 70, an optional voltage dropping resistor 71 and a diode 72 to the terminal 54 The diode 72 is poled to conduct current toward the terminal 54. Another diode 73 is poled to conduct current toward the transformer secondary terminal 42. The lower end of the relay 65 is also connected through a conductor 74 to the upper end of relay 30 and the lower end of this relay 30 is connected through a conductor 75 and the diode 73 to the secondary terminal 42. A filter capacitor 80 is connected across the relay 30 and a filter capacitor 81 is connected across the relay 65.

The diode 72 supplies direct current operating voltages to the amplifier 60 when the manual switch 33 or relay contact 66 is closed. A filter capacitor 82 is connected between the midtap 43 and a terminal 83. A filter resistor 84 is connected between the terminal 83 and a terminal 85 at the junction of the diode 72 and resistor 71. This connection develops a rectified positive direct current voltage at the midtap 43 and a negative direct current voltage at terminal 83.

The amplifier 60 may also include a transistor preamplifier shown by transistor 88. This increases the sensitivity of the entire control system 12. The transistor 88 has a base 89 connected by a bias resistor 90 to the terminal 83. The transistor 88 also has an emitter 91 connected to the midtap 43, and a collector 92 connected to a terminal 93. A load resistor 94 for the transistor 88 is connected between terminals 83 and 93 to receive the collector current of this transistor 88. The potential at terminal 93 is passed by a coupling capacitor 95 to the base 63 of the transistor 64. A self bias resistor 96 is connected between base 63 and emitter 66 of transistor 64. The base 89 of the transistor 88 is connected through a current limiting resistor 87 to the terminal 45 to provide an input to the amplifier 60.

A manual knob 101 moves a pointer 102 cooperating with indicia 103 to indicate the desired directional position of the antenna 14. The knob 101 has an output to a lost motion device shown as a pin 104 and yoke 105, as an example. The yoke 105, after the lost motion is taken up, is connected to move the movable blade 49 of the manual potentiometer 46. The knob 101 also has a direct connection 106 to actuate the manual switches 28 and 33. This connection is such that upon initial movement of the knob 101 and during the take up of the lost motion connection, the first movement opens the normally closed switch 28, next the normally open switch 33 closes and third the lost motion connection is taken up to actuate the movable blade 49. An indicator lamp 107 may be connected across the conductors 26 and 27.

The control system 12 has a terminal strip 110 with five terminals thereon. These are connected to the conductor 26, terminals 31 and 32 and conductors 53 and 50', respectively. A five conductor low voltage cable may interconnect the terminal strip and a corresponding terminal strip 111 in the antenna rotator device 11. This cable may be of any convenient length to interconnect the control system 12 and rotator unit 11.

The above described system provides a remote control of a servomotor, illustrated as a rotator 11, from a remotely positioned control system 12. The control system 12 may control the desired position of the antenna 14 which will rotate to the new position. There is a feedback from the rotator unit 11 to the control system 12 to rebalance the balanceable circuit or bridge 40 and de-energize this bridge or at least terminate the output therefrom to terminate operation of the motor 13 in the rotator unit 11.

In addition, the present invention provides the indicator system 15 which may be a part of the control system 12 or may be added at any later date. For convenience, the indicator system 15 has been shown as a completely separate unit connected to the control system 12 only through a five conductor cable 115. For convenience this cable may be the same low voltage cable as for interconnecting the terminal strips 110 and 111. The five conductor cable 115 interconnects terminals on a terminal strip 116 in the control system 12 and a terminal strip 117 in the indicator system 15. The indicator system 15 may provide a small size indicator device 119 in which case the indicator system 15 will be sufficiently compact to rest upon the top of the television receiver set or any other convenient location desired. Alternatively the indicator device 119 may be a large dial which may be hung on the wall. For example, it might be used with an amateur radio operators equipment and hung on the wall of the ham shack. In this case the indicator system 15 may conveniently be built into the back of the large dial face indicator device 119.

The indicator system 15 is powered from the same alternating current source 21 as powers the control system 12 with power received over the five conductor cable 115. A balanceable circuit or bridge 140 is provided in the indicator system 15. This bridge 140 has an output which controls an indicator motor 121 which in turn drives a pointer 122 to cooperate with indicia 123 on the indicator device 119.

The bridge 140 is quite similar to the bridge 40 in construction and operation and includes a relay and a relay 165 energized by the output of the bridge 140. Relay 130 controls contacts 129 which are single-pole doublethrow contacts to control reversible energization to motor windings 124 and 125. Relay 165 controls normally open contacts 166.

The indicator system 15 includes a transformer 137 having a primary 138 and a secondary 139. This secondary has end terminals 141 and 142 and a midtap 143. The terminals 141 and 142 are the first and second input terminals of the bridge and the upper and lower sections of secondary 139 on either side of the midtap 143 constitute the first and second legs of the bridge 140. The third leg of the bridge 140 is constituted by a first impedance 144 shown as a resistor. A first bridge output terminal 145 is connected to one end of this resistor 144 and the other end thereof is connected to terminal 141. The second output terminal of the bridge 140 is the midtap 143. The output terminals 143 and 145 are connected to an amplifier with components therein the same as the components in amplifier 60 with numerals all being 100 units larger.

The fourth leg of the bridge 140* includes two variable impedance devices. The first variable impedance device is the complementary section 52 of the first potentiometer 46, which is physically located in the control system 12. The second variable impedance device is shown as a third potentiometer 147. This potentiometer has a movable blade 149 moved by the output from the indicator motor 121. The connection of this fourth leg is from the bridge output terminal 145 through a conductor 155, the potentiometer 147, a conductor 150, the terminal strip 117, a conductor of the five conductor cable 115, terminal strip 116, a conductor 152, the complementary section 52 of potentiometer 46, conductor 48, terminal strip 116, a conductor of cable 115, terminal strip 117 and a conductor 153 to the secondary terminal 142. Accordingly it will be seen that the variable impedance device 46 is connected in both the balanceable circuits 40 and 140. The first complementary section 51 of the first potentiometer 46 is connected in the bridge 40 and the second complementary section 52 of the first potentiometer 46 is connected in the bridge 140. Accordingly any change of position of the movable blade 49 will simultaneously and inversely vary the impedance in the bridges 40 and 140.

Power is supplied to the transformer 137 by a conductor 133, through terminal strips 116 and 117 and a conductor 134 to one end of the primary 138. The other end of the primary is connected by the conductor 153 to terminal strips 117 and 116 to the end terminal 42 of secondary 22. Power is supplied to the indicator motor 121 from the secondary 22. A conductor 156 is connected to conductor 26 and through terminal strips 116 and 117 and a conductor 157, through relay contacts 166 to the motor windings 124 and 125. The single-pole double-throw switch 129 is connected by a conductor 158 and conductor 153, terminal strips .117 and 116 to end terminal 42 of secondary 22.'The end terminal 41 of this secondary 22 is connected through the previously mentioned emergency stop switch 56 and conductors 55 and 57 to the conductor 26.

An indicator lamp 207 may be connected across the conductor 153 and a conductor 151 leading to conductor 55 and terminal 41 to provide illumination for the indicator device 119.

Operation of FIGURE 1 The control system 12 may control the position of the rotator unit 11 by causing selected direction of rotation of the motor 13. The manual knob 101 moves the potentiometer blade 49 and this unbalances the bridge 40 to cause an output therefrom. This selectively energizes either the relays 30 and 65 or just the relay 65 and i gether these relay means 30 and 65 control the selected direction of rotation of the motor 13 and energization of bridge 40. This motor 13 rotates to the desired position and in so doing drives the second potentiometer 47. This has a feedback connection to the first bridge 40 to rebalance this bridge and upon rebalance the output from the bridge 40 ceases, to stop rotation of the motor 13. At this time the position of the antenna 14 is oriented with the selected direction of the pointer 102 on knob 101.

Additionally, the indicator system 15 operates substantially in synchronism with the operation of the rotator unit 11 to provide a visual indication of the approximate position of the antenna 14. The indicator motor 121 may be a small reversible induction motor or, since the load is small, may be a reversible synchronous motor. If it is a synchronous motor it will run slightly faster than the inductor motor 13 in the rotator unit 11. Thus the pointer 122 may be slightly ahead of the antenna position, depending upon gearing, but the entire system is such that the bridge 40 balances independently from the balance of the bridge 140 and thus the indicator will shut off in synchronism with the position of the antenna 14.

FIGURE 1 illustrates the knob pointer 102 as pointing roughly toward the northeast. Let it now be assumed that the knob is rotated clockwise in the direction of the arrow to the south position. The movement is first to open the switch 28, next to close the manual switch 33, and when the lost motion connection is taken up, then the potentiometer blade 49 will be rotated to increase the resistance of the section 51 and decrease the resistance of the section 52. It is assumed that the manual switch 20 has previously been closed to energize the transformer 19 and that the bridge 40 was previously balanced at shutoff and that the movement of potentiometer blade 49 unbalanced this bridge 40. Upon the opening of the manual switch 28, the motor 13 is prevented from rotating until the correct direction of rotation is selected. This prevents false starts of rotation of this motor 13 in the wrong direction. Upon the closing of manual switch 33, voltage is supplied from secondary 22 to the terminal 54, to energize the bridge 40, and this, plus the bridge unbalance, establishes an output therefrom. This output energizes the relay 65 to close the relay contacts 66 within about one-tenth of a second after the rotation of the knob 101 and thereafter the knob 101 may be released to open the contact 33 without change in the circuit condition. This will be because the relay contacts 66 have closed in parallel with the manual switch 33 to maintain energized the bridge 40.

The unbalance of the bridge 40 is in a direction caused by the increased impedance in the fourth leg constituted by potentiometer section 51 and the potentiometer 47.

These potentiometers are thus Variable impedance means having first and second sections of concurrently variable impedance, in this case complementary in impedance value. This increases the voltage drop in this fourth leg and accordingly shifts the phase of the potential of output terminal 45 in such a manner that the voltage from output terminal 45 to output terminal 43 is in phase with the input voltage from end terminal 41 to end terminal 42. When terminal 41 is positive, terminal 45 will be positive. Bias resistor establishes a small normal current flow through transistor 88. Accordingly when terminal 45 is positive at the time that terminal 41 is positive, this drives the base 89 of transistor 88 positive to turn oif this transistor 88. The terminal 93 of load resistor 94 is normally positive with reference to terminal 83 from this small current flow through the transistor 88. The turn off of the transistor 88 drives the terminal 93 less positive or more negative, and this negative going signal is passed by the capacitor 95 to the base 63 of transistor 64. This turns on the transistor 64 to have an output signal from the collector 67 to the relay 65. Current through this relay 65 may not flow through diode 72 because terminal 41 is positive during this positive half cycle. Instead it flows through diode 73 to terminal 42, which is negative during this half cycle. Accordingly both relays 65 and 30 are energized during this condition of bridge unbalance. The switch 29 thus moves to engage contact 32 to directly energize motor winding 25 and to energize motor Winding 24 with a leading current through capacitor 36. This provides rotation of the motor 13 in a clockwise direction to rotate the antenna clockwise from the northeast position toward the south position.

During rotation of this motor 13, the potentiometer 47 is driven in a clockwise direction which reduces the impedance thereof. At some point the reduced impedance of the potentiometer 47 will again balance the bridge 40. Upon this balance condition being reached, the bridge will terminate its output and this will de-energize the relay 65 to open contact 66. This will stop the motor 13 in the desired position and also de-energize the bridge 40.

The aforementioned description relates to the control system 12 controlling the rotator unit 11. The knob 101 is described as moving the potentiometer blade 49 through the lost motion connection 104-105. The movement of the movable blade 49 changes the impedance of the potentiometer section 51 and also changes the impedance of potentiometer section 52 in an inverse manner. The section 51 is connected in the bridge 40 and the section 52 is connected in the bridge of the indicator system 15. It will be noted that the secondary 22 is continuously energized so long as switch 20 is closed and accordingly the transformer 137 is also energized continuously. The bridge 140 is also continuously energized and upon a change in the impedance value of potentiometer section 52, this will unbalance the bridge 140. Conversely to the operation of the bridge 40, this is a decrease rather than an increase of impedance in the fourth leg of this bridge 140. This decrease of impedance in the fourth leg shifts the voltage between the output terminals 143 and 145 to be in phase with the input voltage from terminals 141 to 142. Now during the negative half cycles, terminal 142 will be positive relative to terminal 141 and simultaneously terminal 145 will be positive relative to the terminal 143. This positive signal on terminal 145 decreases the normal current flow through transistor 188 and decreases the normal collector current flow through the load resistor 194. This makes the terminal 193 more negative, which negative signal is passed to the base 163 of transistor 164 to turn on this transistor. This transistor current flow is through the relay 165 and diode 172 to the terminal 141 which is negative during this half cycle. Energization of relay 165 closes relay contacts 166 .to energize the indicator motor 129. The non-energization of relay 130 establishes that switch 129 directly energizes motor winding 125 and energizes motor winding 124 with a leading current so that motor 121 rotates clockwise. This drives pointer 122 toward the south position. This clockwise rotation of the pointer 122 coincides with a clockwise rotation of the potentiometer blade 149. This increases the impedance of the potentiometer 147 to increase the impedance in the fourth leg of this bridge 140. At some point a balance of the bridge 140 will be reached and at this balance position the output from the bridge will drop to a minimum or null condition so that relay 165 becomes de-energized. This opens the contacts 166 to de-energize and stop the motor 121. Thus the pointer 122 will be at the south position. The motor 121 may move slightly faster than the motor 13, especially if motor 121 is a synchronous motor and motor 13 is an induction motor. This difference in rotational speed does not matter, because each bridge 40 and 140 is separately balanced, yet each is balanced at a position dependent upon the selected position of potentiometer blade 49 in the first potentiometer 46.

The capacitor 81 in parallel with relay 65 may be made smaller than the capacitor 80 in parallel with relay 30. Accordingly capacitor 81 has a shorter time constant and relay 65 will be the first to pull in. The pull in and drop out characteristics also may be varied by changing the gap on the relay armature as well as the spring tension. Relay 65 being the first to pull in Will close contacts 66 to condition the motor circuit for energization. Relay 30 being the second to pull in will establish the direction of motor rotation. Thus the direction of motor rotation will have been established before the manual switch 28 is closed which actually provides motor current. The relay 65 being the first to drop out will actually open contact 66 and deenergize the motor before relay 30 drops out. This means that there will not be any last second reversal of the motor directional rotation and also means that contacts 29, 31 and 32 may be made light duty contacts since they do not make and break the circuit.

Pull in and drop out specifications may be similarly arranged for relays 130 and 165. With relay 165 the last to pull in and first to drop out, the contacts 166 will actually make and break the current to motor 121, thus relieving contacts 129 of this function.

Now if the knob 101 is rotated counterclockwise to a new position, this moves potentiometer blade 49 counterclockwise to decrease the impedance of potentiometer section 51 and increase the impedance of section 52. The decreased impedance in section 51 decreases the impedance in the fourth leg of bridge 40. This shifts the phase of voltage 43-45 -to be in phase with the voltage 41-42. Thus during negative half cycles when terminal 41 is positive, output terminal 45 is positive. This applies a positive voltage on base 89 of transistor 88 to turn otf transistor 88 and turn on transistor 64. Collector current from transistor 64 flows through relay 65 and diode 72 to terminal 41, which is negative at that time. This energizes only relay 65 and not relay 30. Accordingly upon the closing of relay contacts 66, motor winding 24 is energized directly and motor winding 25 is energized with a leading current for counterclockwise rotation of the motor 13. This drives the antenna in a counterclockwise direction to the new desired location.

counterclockwise rotation of motor 13 also drives potentiometer 47 counterclockwise to increase the impedance thereof. This will continue until bridge 40 is balanced whereupon output therefrom drops to a minimum or null to de-energize relay 65. This opens contacts 66 to de-energize motor 13 and also the bridge 40.

Concurrently the manual movement of potentiometer blade 49 counterclockwise not only decreased the impedance of potentiometer section 51, but also increased in inverse ratio the impedance of potentiometer section 52. This increase of impedance of potentiometer section 52 increased the impedance in the fourth leg of bridge to unbalance same. Since this bridge is continuously energized, this unbalance is in a direction to make the voltage 143-145 in phase with the voltage 142-141. Thus during positive half cycles when terminal 141 is positive, terminal 145 is also positive. During these positive half cycles the base 189 of transistor 188 is driven positive to turn off this transistor thus turning on transistor 164, and the transistor collector current passes through relays and 130 and diode 173 to terminal 142 which is negative during this half cycle. This energizes both relays 165 and 130 with relay 130 pulling in first to select the desired counterclockwise direction of rotation of indicator motor 121. Relay 165 pulls in second to close contacts 166 and effect actual energization of motor 121. Rotation of this motor 121 drives the pointer 122 counterclockwise and also drives the potentiometer blade 149 counterclockwise to a position of balance. The balance will be reached when the decreased impedance of potentiometer 147 matches the increased impedance of potentiometer section 52. Upon balance relay 165 drops out to open contacts 166 and de-energize motor 121.

The potentiomcters 46, 47 and 147 may be the type permitting a full 360 degrees of rotation from maximum to minimum impedance or they may be the type which has about 300 degrees of rotation between stops. In the latter case, the gearing to the actuating motors will be such as to permit 360 degree rotation of the antenna 14 or pointer 122 for the 300 degree rotation of the associated potentiometers.

It will be noted that control system 12 and rotator unit 11 form a complete remotely controlled servomotor with a closed loop feedback system. Thus these two units 11 and 12 are completely operable by themselves. Accordingly an antenna rotator system embodying this invention may be manufactured and sold and provided with terminal strip 116. Thus a user may purchase the indicator system 15 separately at any time and add it to the rotator unit and control system. The only interconnections necessary are to interconnect the terminal strips 116 and 117 by commonly available low voltage five conductor cable. Also the indicator system 15 may be a small table top model with a small indicator device 119 or may be a large wall hung model. The indicator motor 121 may be a small clock type synchronous motor requiring only a lower power input such as 2 to 5 watts, which power will place a negligible drain on the secondary 22.

It does not matter whether the bridge 40 is balanced before or after the bridge 140. Movement of potentiometer 47 balances bridge 40 and movement of potentiometer 147 balances bridge 140. The two systems, namely control system 12 and indicator system 15, are separately balanced and will shut off independently of the other. The shut off will establish the pointer 122 in synchronism with the position of the antenna 14, this despite the fact there might be a slight variation in speed of motors 13 and 121. In both cases it is the movement of potentiometer r 9 blade 49 which establishes the initial unbalance of the two bridges and this unbalance is effected in an inverse manner for the two bridges.

If wind or other force on the antenna 14 should move the potentiometer 47, this will not start the indicator system 15. The reason is that the birdge 40 is normally not energized until manually energized by manual switch 33 through actuation of the knob 101. Thus this prevents annoying starts and stops of the indicator pointer 122 such as might occur during a wind storm.

The emergency stop switch 56 is provided to stop the rotator at any desired time, regardless of the fact that the bridge 40 may not be balanced. Also, this emergency stop button stops the indicator system 15 so that the pointer 122 will indicate the approximate position of the antenna. This may be desirable in many cases. For example, if the direction of the received signal is not known and the radio operator is merely rotating the antenna trying to locate the position of strongest received signal, once this strongest signal is received, the operator may press the emergency stop switch 56. This de-energizes the bridge 40 and de-energizes motor 13. De-energization of bridge 40 makes relay 65 drop out to open contact 66 thereof. Thus even when the push button 56 is released, bridge 40 will not become re -energized. Also opening of the switch 56 de-energizes the transformer 137 in the indicator system 15. This shuts down this entire indicator system 15, dropping out relay 165. When the switch 56 is reclosed, this will re-energize the indicator bridge 140. However, the operator will have observed the present position of the antenna 14 by observing the pointer 122 and thus the knob 101 may be reset to coincide with the position of pointer 122. This will enable manual rebalance of bridge 40 and of bridge 140.

FIGURE 2 shows a modified schematic diagram of a control system 12A controlling the antenna rotator 11 and having an indicator system 15A optionally connectable thereto by the five conductor cable 115. The antenna rotator 11 may be the same as in FIGURE 1. The control system 12A and the indicator system 15A are similar but somewhat different. In the control system 12A the bridge 40 and the amplifier 60 may be identical to those shown in FIGURE 1 and accordingly the internal wiring of the amplifier 60 has not been shown. The circuit elements and connections thereto which are common between the control system 12 of FIGURE 1 and the control system 12A of FIGURE 2 will not be described, reference being made to the description above in connection with FIGURE 1.

In the control system 12A of FIGURE 2 the transformer primary 18 is shown as being always energized from the voltage source 21, without a switch in the primary circuit. The emergency stop switch 56 is connected directly to line 57 and line 133, without any separate conductor 151 being provided. A conductor 210 is provided from terminal 42 to the terminal strip 116. A manually controlled switch 233 is also connected to terminal 42 and then to a conductor 211 and to another terminal on the terminal strip 116. Manual switch 233 is controlled for actuation directly with the knob 101. Switch 233 is a normally open switch and closes preferably at the same time as manual switch 33.

The indicator system 15A includes a bridge 140 and an amplifier 160 which may be identical with the counterparts in FIGURE 1. In the indicator system 15A conductor 134 connects to conductor 133 and to end terminal 141 on an inductive winding 139A. This may have a magnetic core 137A, however no actual transformer is supplied as in FIGURE 1, and this is a simplification in the circuit of FIGURE 2. Conductor 210, after passing through the terminal strips 116 and 117, is connected through the relay contacts 166 and then the conductor 153 and to the lower end terminal 142 of the inductive winding 139A. Conductor 211 extends through the terminal strips 116 and 117 and also connects to this conductor 10 153. In conductor 157 the relay contacts 166 have been omitted.

Operation of FIGURE 2 With the emergency stop switch 56 in closed position, the transformer 19 is energized as is the secondary 22 and secondary 23. Upon turning the knob 101 clockwise to a new desired position for the antenna 14, this first opens manual switch 28 to prevent false direction starts of the mot-or 13. Next manual switches 33 and 233 are closed. Thirdly, the manual potentiometer blade 49 is moved clockwise to increase the resistance in section 51 and decrease the resistance in section 52. These sections are complementary impedance sections connected in the bridges 40 and 140, respectively. The closing of manual switch 33 energizes the bridge 40 and because of the change of impedance in potentiometer section 51, the bridge 40 is unbalanced and will have an output on positive half cycles to energize both relays 65 and 30. This will close relay contacts 66 within about 50 to milliseconds to maintain the bridge 40 energized. Whether or not relay 30 is energized depends upon the direction of unbalance of the bridge, and as in FIGURE 1, it is assumed that this unbalances the bridge 40 in a direction to cause energization of relay 30. This means that relay contacts 29 engage the contact 32 for direct energization of motor winding 25 and leading current energization to motor winding 24. This causes clockwise rotation of motor 13 and of potentiometer 47. As in FIGURE 1, the bridge 40 will be rebalanced when the antenna 14 and potentiometer 47 reach the desired position.

The closing of manual switch 233 upon the initial turning of the knob 101 will supply power to energize the inductive winding 139A, as well as the bridge 140 and amplifier 160. The changing impedance in potentiometer section 52 will unbalance the bridge 140 causing an output therefrom and energization of relay 165. This will close relay contacts 166 to maintain energized the indicator system 15A even after opening of manual switch 233 upon release of knob 101. As in the description of FIG- URE 1, it is assumed that the decreasing impedance of potentiometer section 52 causes unbalance of the bridge 140 in a direction which does not energize relay 130 and accordingly motor winding 125 is energized directly and winding 124 is energized with a leading current for clockwise rotation of the motor 121. This will rotate the pointer 122 and the potentiometer blade 149 clockwise to a position of balance of the bridge 140. When this occurs, the relay will drop out to d e-energize the indicator system 15A.

If the emergency stop switch 56 is opened at any time during rotation of the motor 13, this will de-energize the bridge 40 and amplifier 60 in the control system 12A to stop motor 13. Also it de-energizes the complete indicator system 15A to stop the indicator motor 121. Preferably this emergency stop switch 56 is a latching or toggle type switch which must be manually reset to the closed condition in order to render the control system operative. This will give a definite indication to the operator that the system has been shut down out of synchronism and that the knob 101 should be turned to reorient the antenna and to synchronize the position of antenna 14 with the position of the indicator 122.

The circuit of FIGURE 2 has the advantage of normally having the indicator system 15A completely deenergized and it is only energized upon closing of the manual switch 233.

FIGURE 3 illustrates still another modification of the invention. This figure shows an antenna rotator 11B which is similar to but slightly difierent from the rotator unit 11 of FIGURE 1. FIGURE 3 also shows a control system 128 and an indicator system 15B which are similar to but slightly different from the counterparts in FIGURE 1. In the control system 12B there is a bridge 408 which is slightly different from the counterpart in FIGURE 1. An amplifier 60 is provided which may be identical to that in 11 FIGURE 1. In this FIGURE 3 only those circuit elements and connections which are different from those in FIG- URE 1 will be hereinafter described. FIGURE 3 provides no connection such as conductor 57 of FIGURE 1, and instead the bridge 40B is permanently connected tothe secondary 22 by a conductor 240 interconnecting terminals 54 and 41. The manual potentiometer 46 has been changed to use only one section thereof instead of complementary sections. Conductor 50 extends from the lower right terminal of potentiometer 46 to a lower left end terminal of the motor driven potentiometer 47. This potentiometer 47 is now the variable impedance means having first and second complementary impedance sections 251 and 252 connected in the control bridge and indicator bridge, respectively. The movable blade 249 of potentiometer 47 is connected by a conductor 241 through the terminal strip 111 to the conductor 53. The right end terminal of potentiometer 47 is connected by a conductor 242 to the common connection of motor windings 24 and 25.

A conductor 243 is connected to the end terminal 41 of the secondary 22 and connects to a terminal on terminal strip 116. A conductor 210 interconnects secondary end terminal 42 with a second terminal on terminal strip 116. Conductor 156 connects conductor 26 with a third terminal on the terminal strip 116. A conductor 244 connects conductor 53 with a fourth terminal on terminal strip 116.

The indicator system B is changed slightly from that shown in FIGURE 1. One change is that only four terminals on the terminal strips 116 and 117 need be used. Conductor 134 leads from the first terminal -on terminal strip 117 to the upper terminal on primary 13$. Conductor 153 connects the second terminal of terminal strip 117 with the lower terminal of primary 138. Conductor 155 connects the third terminal of terminal strip 117 and terminal 142. Conductor 150 interconnects the fourth terminal of terminal strip 117 and the left end terminal of potentiometer 147. The motor 121 is energized directly across the secondary 139 through conductors 157 and 158 and through relay contacts 166 connected in the conductor 157. The indicator lamp 207 is connected across conductors 134 and 153.

Operation 0) FIGURE 3 Assuming that switch is closed the transformer 19 will be energized to energize secondaries 22 and 23. The bridge 40B and amplifier 60 will be energized at this time. The transformer 137 of indicator system 1513 will also be energized to energize bridge 140B and amplifier 160. If the knob 101 is now rotated clockwise, this first opens switch 28 to prevent initial rotation of motor 13. Next switch 33 is closed to condition the motor energization circuit upon output from the bridge 40B. Rotation of the potentiometer blade 49 clockwise decreases the impedance in this potentiometer 46 and unbalances the bridge 40B. Accordingly there will be an output therefrom to energize relay 65 and close contact 66 to effect motor energization in accordance with the selected direction of rotation, depending upon whether or not relay is energized. The motor 13 will rotate clockwise to rotate the antenna 14 and potentiometer blade 249 clockwise. This incrcases the impedance in potentiometer section 251 to gradually re-establish balance in the bridge 4013.

The motor driven clockwise movement of potentiometer blade 249 will decrease the impedance in potentiometer section 252. This will unbalance the bridge 140B and produce an output from amplifier 160 to energize re lay 165. This closes relay contacts 166 to energize the indicator motor 121 and drive the pointer 122 in a selected direction, in this example, a clockwise direction. This also drives the movable blade 149 clockwise to increase the impedance in potentiometer 147 and this gradually re-establishes balance of the bridge 140B.

Each bridge B and 1408 is separately balanced depending upon the complementary impedance sections 251 and 252 of the potentiometer 47. It will be noted that in this circuit of FIGURE 3 the indicator system 15B is dependent for rebalance upon a change of impedance caused by the motor driven potentiometer 47 rather than a change of impedance in the manual potentiometer 46. Thus in this circuit of FIGURE 3 the indicator pointer 122 follows the actual position of the antenna 14. Should the antenna be iced, for example, and fail to rotate, then the indicator pointer 122 will also fail to rotate and this will inform the operator that the rotator is not operating properly. Also this FIGURE 3 circuit is one wherein the motor driven potentiometer actually sends two separate feedback signals, one to the control system 12B and the other to the indicator system 15B.

The manual switch 20 may be used as an emergency stop switch. If it is opened the entire circuit will become de-energized to stop both motors 13 and 121 even though they may previously have been moving.

The present disclosure includes that contained in the appended claims, as well as that of the forgoing description.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of the circuit and the combination and arrangement of circuit elements may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

What is claimed is:

1. A control system, comprising, in combination, first ant second balanceable circuits each having an output,

an indicator,

said second circuit having an output to said indicator,

variable impedance means having first and second concurrently variable impedance sections,

means connecting said first and second sections in said first and second circuits, respectively,

means including said impedance means to affect the balance of said first circuit and upon unbalance establishing an output from said first circuit,

a variation in impedance of said impedance means also unbalancing said second circuit to establish output therefrom,

means connecting the output of said first circuit to effect rebalance of said first circuit to terminate output from said first circuit,

and means connecting the output of said second circuit to effect rebalance of said second circuit to terminate output from said second circuit.

2. A control system comprising, in combination, first and second balanceable circuits each having an output,

an indicator,

said second circuit having an output to said indicator,

variable impedance means having first and second concurrently variable impedance sections,

connecting means connecting said first and second sections in said first and second circuits, respectively,

means including said impedance means to affect the balance of said first circuit,

first means to establish an output from said first circuit upon unbalance of said first circuit and said first clrcuit connected to maintain the output from said first circuit after deactuation of said first means,

a variation in impedance of said impedance means also unbalancing said second circuit to maintain the output from said second circuit after deactuation of said first means,

means connecting the output of said first circuit to effect rebalance of said first circuit to terminate output from said first circuit,

and means connecting the output of said second circuit to effect rebalance of said second circuit to terminate output from said second circuit.

3. A control system comprising, in combination, first and second balanceable circuits each having an output,

an indicator,

said second circuit having an output to said indicator,

variable impedance means having first and second concurrently variable impedance sections,

means connecting said first and second sections in said first and second circuits, respectively,

switch means,

means including said switch means and said impedance means to affect the balance of andoutput from said first circuit and upon unbalance establishing an output from said first circuit after opening of said switch means,

a variation in impedance of said impedance means also varying the impedance of said second section and unbalancing said second circuit to maintain the output from said second circuit after opening of said switch means,

means connecting the output of said first circuit to effect rebalance of said first circuit to terminate output from said first circuit,

and means connecting the output of said second circuit to effect rebalance of said second circuit to terminate output from said second circuit.

4. A control system comprising, in combination, drive means,

a first balanceable circuit,

an indicator,

a second balanceable circuit having an output to said indicator,

multi-terminal variable impedance means having first and second sections between pairs of terminals,

means connecting said first and second sections in said first and second circuits, respectively means connected to vary the impedance of said impedance means,

switch means actuatable to establish an output from said first circuit,

means including said impedance means to effect the balance of said first circuit and upon unbalance establishing an output from said first circuit,

a variation in impedance of said impedance means also varying the impedance of said second section and unbalancing said second circuit to maintain the output from said second circuit after opening of said switch means,

means connecting said drive means to effect rebalance of 'said first circuit to terminate output from said first circuit and de-energize said drive means,

and means connecting the output of said second circuit to effect rebalance of said second circuit to terminate output from said second circuit.

6. A control system comprising, in combination, drive means controlled by a first balanceable circuit,

an indicator,

2. second balanceable circuit having an output to said indicator,

multi-terminal variable impedance means having first and second sections between pairs of terminals,

means connecting said first and second sections in said first and second circuits, respectively,

manual means connected to vary the impedance of said impedance means,

manual switch means moved in accordance with said manual means to establish an output from said first circuit,

a variation in impedance of said impedance means causing unbalance of and output from said first circuit to maintain the output from said first circuit after opening of said manual switch means to effect operation of said drive means,

a variation in impedance of said impedance means also unbalancing said second circuit to maintain the output from said second circuit after opening of said manual switch means,

means. connecting said drive means to effect rebalance of said first circuit to terminate output from said first circuit and de-energize said drive means,

and means connecting the output of said second circuit to effect rebalance of said second circuit to terminate output from said second circuit.

7. A control system comprising, in combination, drive means,

a first phase sensitive circuit,

an indicator,

a second phase sensitive circuit having relay means connected to control energization to said indicator,

a three terminal variable impedance device having first and second sections between pairs of terminals,

means connecting said first and second sections in said first and second phase sensitive circuits, respectively,

manual means connected to vary the impedance of said impedance device,

manual switch means moved in accordance with said manual means to establish an output from said first phase sensitive circuit,

a variation in impedance of said impedance device causing unbalance of and output from said first phase sensitive circuit to maintain the output from said first phase sensitive circuit after opening of said manual switch means to effect operation of said drive means,

a variation in impedance of said impedance device also unbalancing said second phase sensitive circuit to energize said relay means to energize said second drive means,

means connecting said drive means to effect rebalance of said first phase sensitive circuit to terminate output from said first phase sensitive circuit and deenergize said drive means,

and means connecting the output of said second cir cuit to effect rebalance of said second phase sensitive circuit to tie-energize said relay means.

8. A control system comprising, in combination, first drive means,

a first phase sensitive circuit,

an indicator,

second drive means connected to drive said indicator,

a second phase sensitive circuit having relay means connected to control energization to said second drive means,

a potentiometer having first and second sections,

means connecting said first and second sections in said first and second phase sensitive circuits, respectively,

manual means connected to move said potentiometer,

manual switch means moved in accordance with said manual means to establish an output from said first phase sensitive circuit,

movement of said potentiometer causing unbalance of and output from said first phase sensitive circuit to maintain the output from said first phase sensitive circuit after opening of said manual switch means to effect operation of said first drive means,

the movement of said potentiometer also unbalancing said second phase sensitive circuit to energize said relay means to energize said second drive means,

means connecting said first drive means to effect rebalance of said first phase sensitive circuit to terminate output from said first phase sensitive circuit and deenergize said first drive means,

and means connecting said second drive means to effect rebalance of said second phase sensitive circuit to de-energize said relay means to de-energize said second drive means.

9. A control system comprising, in combination, first drive means,

a first phase sensitive circuit,

first relay means controlled by the output of said circuit and connected to control energization to said drive means,

an indicator,

second drive means connected to drive said indicator,

a second phase sensitive circuit having relay means connected to control energization to said second drive means,

a potentiometer having first and second sections,

means connecting said first and second sections in said first and second phase sensitive circuits, respectively,

a manual knob connected to move said potentiometer,

manual switch means moved in accordance with said knob to establish an output from said first phase sensitive circuit,

movement of said knob also moving said potentiometer to unbalance said first phase sensitive circuit and energize said first relay means to maintain the output from said first phase sensitive circuit after opening of said manual switch means upon release of said knob,

means to establish an output from said second phase sensitive circuit,

the movement of said potentiometer also unbalancing said second phase sensitive circuit to energize said second relay means to energize said second drive means,

means connecting said first drive means to effect rebalance of said first phase sensitive circuit to deenergize said first relay means to terminate output from said first phase sensitive circuit and de-energize said first drive means,

and means connecting said second drive means to effect rebalance of said second phase sensitive circuit to de-ener-gize said second relay means to de-energize said second drive means.

10. A control system comprising, in combination, first drive means,

a first phase sensitive circuit,

first relay means controlled by the output of said circuit and connected to control energization to said drive means and to said circuit,

an indicator,

second drive means connected to drive said indicator,

a second phase sensitive circuit having relay means connected to control energization to said second drive means,

first manual switch means connected to control energization to said first phase sensitive circuit,

a potentiometer having first and second sections,

means connecting said first and second sections in said first and second phase sensitive circuits, respectively,

a manual knob connected to move said potentiometer,

second manual switch means moved in accordance with said knob to energize said first phase sensitive circuit,

movement of said knob also moving said potentiometer to unbalance said first phase sensitive circuit and energize said first relay means to maintain said first phase sensitive circuit energized after opening of said second manual switch means upon release of said knob,

means to effect energization of said second phase sensitive circuit, the movement of said potentiometer also unbalancing said second phase sensitive circuit to energize said second relay means to energize said second drive means,

means connecting said first drive means to effect re- :balance of said first phase sensitive circuit to deenergize said first relay means to de-energize said first phase sensitive circuit and de-energize said first drive means,

and means connecting said second drive means to effect rebalance of said second phase sensitive circuit to deenergize said second relay means to de-energize said second drive means.

11. A control system comprising, in combination, re-

versible output drive means,

a first phase sensitive circuit,

first relay means controlled by the output of said circuit and having contact means connected to control energization to said drive means and to said circuit,

an indicator,

second reversible output drive means connected to drive said indicator,

a second phase sensitive circuit having second relay means with contact means connected to control energization to said second drive means,

first manual switch means connected to control energization to said first and second phase sensitive circuits,

a potentiometer having first and second sections,

means connecting said first and second sections in said first and second phase sensitive circuits, respectively,

a manual knob connected to move said potentiometer,

second manual switch means moved in accordance with said knob to energize said first phase sensitive circuit,

movement of said knob also moving said potentiometer to unbalancesaid first phase sensitive circuit and energize said first relay means to maintain said first phase sensitive circuit energized after opening of said second manual switch means upon release of said knob,

the movement of said potentiometer also unbalancing said second phase sensitive circuit to energize said second relay means to energize said second drive means,

means connectng said first drive means to effect rebalance of said first phase sensitive circuit to de-energize said first relay means to de-energize said first phase sensitive circuit and tie-energize said first drive means,

and means connecting said second drive means to effect rebalance of said second phase sensitive circuit to de-energize said second relay means to de-energize said second drive means.

12. A control system comprising, in combination,

drive means having a reversible output,

a first phase sensitive circuit having an input energizable from alternating current source means and having an output,

first relay means controlled by the output of said circuit and having first contact means,

means connecting said first contact means to control energization to said drive mean and to said first circuit,

an indicator,

second reversible output drive means connected to drive said indicator,

a second phase sensitive circuit having an input and having an output,

second relay means controlled by the output of said second circuit and having second contact means,

means connecting said second contact means to control energization to said second drive means,

a first manual switch connected to control energization from said alternating current source means to said first phase sensitive circuit,

a potentiometer having first and second sections,

means connecting said first and second sections in said first and second phase sensitive circuits, respectively,

a manual knob connected to move said potentiometer,

a second manual switch moved in accordance with said knob to disable energization of both said drive means,

a third manual switch actuated closed in accordance with movement of said knob to energize said first phase sensitive circuit,

movement of said knob also moving said potentiometer t-o unbalance said first phase sensitive circuit and energize said first relay means and to close said 17 first contact means to maintain said first phase sensitive circuit energized after opening of said third manual switch upon release of said knob,

the movement of said-potentiometer also unbal-ancing said second phase sensitive circuit to energize said second relay means and close said second contact means to energize said second drive means,

means connected to be operated in accordance with said first drive means to effect rebalance of said first phase sensitive circuit to de-energize said first relay means and open said first contact means to de-energize said first phase sensitive circuit and deenergize said first drive means,

and means connected to be operated in accordance with said second drive means to efiect rebalance of second phase sensitive circuit to de-energize said second relay means and open said second contact means to de-energize said second drive means.

13. An indicator and follow-up control system for drive means having an output, comprising, in combination.

first and second bridges each having an input and an output,

a potentiometer connected in said first and second bridges,

means connecting the output of said first bridge to control the movement of said drive means,

a change of impedance of said potentiometer unbalancing said first bridge to establish controlled movement of said output of said drive means,

means connecting said output of said drive means as a follow-up toward rebalance of said first bridge,

an indicator device,

second drive means connected to drive said indicator device,

means connecting the output of said second 'bridge to control the movement of said second drive means,

a change of impedance of said potentiometer also unbalancing said second bridge to establish controlled movement of said output of said second drive means,

and means connecting said output of said second drive means as a follow-up toward rebalance of said second bridge.

14. A remote indicator and follow-up control system for drive means having a reversible output, comprising, in combination,

first and second balanceable alternating current bridges each having an input energizable from alternating current source means and each having an output,

first and second potentiometers connected in said first bridge,

means connecting the output of said first bridge to control the movement of said drive means,

a change of impedance of said first potentiometer unlbalancing said first bridge to establish controlled movement of said reversible output of said drive means,

means connecting said second potentiometer for movement in accordance with movement of said output of said drive means as a follow-up toward rebalance of said first bridge,

a remote indicator device,

second reversible output drive means connected to drive said indicator device,

a third potentiometer,

means connecting said first and third potentiometers in said second bridge,

means connecting the output of said second bridge to control the movement of said second drive means,

a change of impedance of said first potentiometer also unbalancing said second bridge to establish controlled movement of said output of said second drive means,

and means connecting said third potentiometer for movement in accordance with movement of said out- 18 put of said second drive means as a follow-up toward rebalance of said second bridge.

15. A remote indicator and follow-up control system for first drive means having a reversible output comprising, in combination,

first and second balanceable alternating current bridges each having an input energizable from alternating source means and each having an output,

first, second and third potentiometers,

said first potentiometer 'having first and second complementary sections with concurrently and inversely changeable impedance,

means connecting said second potentiometer and the first section of the first potentiometer in said first bridge,

means connecting said third potentiometer and said second section of said first potentiometer. in said second bridge,

manual switch means to establish energization of said first and second bridges from said alternating current source means,

means connected to the output of said first bridge controlling the energization to said drive means and maintaing energization to said first bridge,

a change of impedance of said first potentiometer unbalancing said first bridge to establish an output therefrom and to establish selected directional movement of the output of said drive means,

means connecting said second potentiometer for movement in accordance with movement of said output of said drive means as a follow-up toward rebalance of said first bridge,

a remote indicator device,

second reversible output drive mean-s connected to drive said indicator device,

means connected to the output of said second bridge to effect energization to said second drive means,

.a change of impedance of said second section of said first potentiometer also unbalancing said second bridge to establish an output therefrom and to establish selected directional movement of the output of said second drive means,

and means connecting said third potentiometer for movement in accordance with movement of said output of said second drive means as a follow-up to- -ward rebalance of said second bridge.

16. A remote indicator and follow-up control system for first drive means having a reversible output comprising, in combination,

first and second balanceable alternating current bridges each having an input energizable from alternating current source means and each having an output,

first, second and third potentiometers,

said first potentiometer having a movable blade to concurrently and inversely change the impedance of first and second complementary sections thereof,

means connecting said second potentiometer and the first section of the first potentiometer in said first bridge,

means connecting said third potentiometer and said second section of said first potentiometer in said second bridge,

first and second relay means controlled in energization from the output of said first and second bridges, respectively,

manual switch means to establish energization of said first and second bridges from said alternating current source means,

normally open contact means on said first relay means of said first bridge controlling the energization to said drive means and maintaining energization to said first bridge,

movement of said movable blade of said first potentiometer unbalancing said first bridge to energize said first relay means and to establish selected directional movement of said drive means,

means connecting said second potentiometer for movement in accordance with movement of said out-put of said drive means as a follow-up toward rebalance of said first bridge,

a remote indicator device,

second reversible output drive means connected to drive said indicator device,

normally open contact means of said second relay means connected to efiect energization of said second drive means,

movement of said movable blade of said first potentiometer also unbalancing said second bridge to energize said second relay means therein and to establish selected directional movement of the output of said second drive means,

and means connecting said third potentiometer for movement in accordance with movement of said output of said second drive means as a follow-up toward rebalance of said second bridge.

17. A remote indicator and follow-up control system for first drive means having a reversible output comprising, in combination,

first and second balanceable alternating current bridges each having an input energizable from alternating current source means and each having an output, first, second and third potentiometers,

said first potentiometer having a movable blade to concurrently and inversely change the impedance of first and second complementary sections thereof,

means connecting said second potentiometer and the first section of the first potentiometer in said first bridge,

means connecting said third potentiometer and said second section of said first potentiometer in said second bridge,

first and second relay means controlled in energization from the output of each said bridge,

manual switch means to establish energization of said first and second bridges from said alternating current source means,

normally open contact means on said first relay means of said first bridge controlling the energization to said drive means and maintaining energization to said first bridge,

contact means on said second relay means of said first bridge connected for selected bi-direction al rotation of said drive means,

movement of said movable blade of said first potentiometer unbalancing said first bridge to energize at least one of said relay means therein to establish selected directional movement of said drive means,

means connecting said second potentiometer for movement in accordance with movement of said output of said drive means as a follow-up toward rebalance of said first bridge,

a remote indicator device,

second reversible output drive means connected to drive said indicator device,

normally open contact means of said first relay means of said second bridge connected to elfect energization of said second drive means, contact means of said second relay means in said second bridge connected for selected bi-directional rotation of the output of said second drive means,-

movement of said movable blade of said first potentiometer also unbalancing said second bridge to energize at least one of said relay means therein to establish selected directional movement of the output of said second drive means,

and means connecting said third potentiometer for movement in accordance with movement of said output of said second drive means as a follow-up toward rebalance of said second bridge.

18. A remote indicator and follow-up control system as claimed in claim 17, including means connecting said second bridge for energization in accordance with energization of said first relay means of said second bridge.

19. A remote indicator and follow-up control system for drive means having a reversible output comprising, in combination, a first and a second balancea-ble alternating current bridge each having two output terminals,

means to energize each said bridge from alternating current source means,

first and second relay means in each bridge,

means including normally open contacts controlled by said first relay means in said first bridge connected to control the output from said first bridge,

means including contact means of said second relay means connected for selective bi-directional rotation of the output of said drive means,

first, second and third potentiometers,

means connecting said first and second potentiometers in said first bridge,

means connecting said first and third potentiometers in said second bridge,

first and second rectifiers connected in each bridge and oppositely poled for conduction on opposite half cycles of the voltage of the alternating current source means,

a transistor amplifier in each bridge,

means connecting the output of each said bridge to the input of the respective amplifier,

means in each bridge connecting the output of the respective amplifier through said first rectifier to said alternating current source means to energize said first relay means upon movement of said first potentiometer in a first direction to unbalance the respective bridge output in a first direction to cause conduction of the respective amplifier on a first one of first and second half cycles of the alternating current source voltage,

means in each bridge for connecting the output of the respective amplifier through said second rectifier to said alternating current source means to energize said second relay means upon movement of said first potentiometer in the second direction to unbalance the respective bridge output in a second direction to cause conduction of the respective amplifier on a second one of first and second half cycles of the alternating current source voltage,

means connecting said second potentiometer to be moved in accordance with movement of the output of said drive means as a follow-up to terminate movement of said drive means upon rebalance of said first bridge,

a remote indicator,

a second reversible drive means connected to drive said indicator,

means including normally open contacts controlled by by said first relay means in said second bridge to control energization to said second bridge,

means including contact means of said second relay mean-s in said second bridge connected for selective bi-directional rotation of the output of said second reversible drive means,

and means connecting said third potentiometer to be moved in accordance with movement of the output of said second drive means as a follow-up to effect rebalance of said second bridge and to terminate move ment of said second drive means.

No references cited.

NEIL C. READ, Primary Examiner.

THOMAS A. HABECKER, Examiner. 

1. A CONTROL SYSTEM, COMPRISING, IN COMBINATION, FIRST ANT SECOND BALANCEABLE CIRCUITS EACH HAVING AN OUTPUT, AN INDICATOR, SAID SECOND CIRCUIT HAVING AN OUTPUT TO SAID INDICATOR, VARIABLE IMPEDANCE MEANS HAVING FIRST AND SECOND CONCURRENTLY VARIABLE IMPEDANCE SECTIONS, MEANS CONNECTING SAID FIRST AND SECOND SECTIONS IN SAID FIRST AND SECOND CIRCUITS, RESPECTIVELY, MEANS INCLUDING SAID IMPEDANCE MEANS TO AFFECT THE BALANCE OF SAID FIRST CIRCUIT AND UPON UNBALANCE ESTABLISHING AN OUTPUT FROM SAID FIRST CIRCUIT, A VARIATION IN IMPEDANCE OF SAID IMPEDANCE MEANS ALSO UNBALANCING SAID SECOND CIRCUIT TO ESTABLISH OUTPUT THEREFROM, MEANS CONNECTING THE OUTPUT OF SAID FIRST CIRCUIT TO EFFECT REBALANCE OF SAID FIRST CIRCUIT TO TERMINATE OUTPUT FROM SAID FIRST CIRCUIT, AND MEANS CONNECTING THE OUTPUT OF SAID SECOND CIRCUIT TO EFFECT REBALANCE OF SAID SECOND CIRCUIT TO TERMINATE OUTPUT FROM SAID SECOND CIRCUIT. 